Opinions on pre-amp tubes concerning OD tone.

Hey there. So I bought a pre amp/OD unit. It is the Blue Tube RT904. Rack mount, spiffy littly thing. What I like about is that it has line level I/O as well as instrument, so that i can stick in my effects loop and rack it. However I am not to happy with the results I am getting. My first thought is to change the pre-amp tube. 12AX7 I believe. Will be opening it up to see whats in side in the next hour or so. So my question is, what tubes do you all like for OD? A nice drive or distortion is what I am after and right now its a little buzzy. I like the JJ's in my 400+ but maybe there are better choices when pushing the tube into clipping.

I really like the Groove Tubes Mullard 12AX7 I just installed in my tube pre. I'd check out Torres Engineering's info on tubes, and I'd highly recommend ordering from them. Good prices, and my tubes got here in 2 days.

i've tried JJs, Groovetubes, and stock sovteks. Searching for basically the most gain/tone i could get.

Well, i bought an Electro-Harmonix 12AX7 tube, and MY GOD, at the same volume, the output is like doubled. The tone is much much thicker and sweeter. So now, for pre-amp tubes, i live by these, and for Power tubes JJ 6L6.